Method for obtaining a mark on a low surface energy ophthalmic lens

ABSTRACT

A method for marking an ophthalmic lens with a hydrophobic and/or oil-repellent low surface energy outer layer on a high surface energy substrate or coating. The method consists in: positioning a complementary patterning mask of the desired marking between the lens surface to be marked and an energizing discharge source capable of substantially eliminating the outer layer to as to expose the subjacent high energy substrate or coating. The temporary protective layer has a surface energy higher than that of the outer layer and a thickness less than about 5 nm, and preferably between 2 and 4 nm, thereby enabling the discharge to act on the outer layer through the temporary protective layer.

The present invention relates to marking ophthalmic lenses, and inparticular eyeglass lenses, for identifying the source, the manufacturerand/or the technical characteristics of the lens, as well as forapplying distinctive signs such as a logo. Such marks are known as“monograms”. There are many methods for marking ophthalmic lenses, someof which involve removing material from the ophthalmic lens and/or thecoatings thereof, in particular by etching or by means of lasers, and inparticular by means of excimer lasers.

The latest generation ophthalmic lenses usually include a hydrophobicand/or oleophobic surface coating to resist smudge associated with anantireflection coating. The antireflection coating, which may comprise asingle layer or multiple layers, consists of a material of high surfaceenergy. A thin protection layer of a low surface energy organic materialis deposited on this antireflection coating. This thin layer reducesoily deposits and other forms of soiling and in practice constitutes ahydrophobic and/or oleophobic surface coating.

Marks of the above kind are preferably invisible under normalcircumstances so as not to irritate the wearer. They are renderedvisible by misting the lens, the thin film of condensation that forms onthe surface producing microdroplets on the low surface energy portions,whereas on the high surface energy portions the film of condensationspreads over the whole of the surface, forming larger droplets. Inambient lighting, diffusion by the microdroplets produces a much lightertone than the larger droplets.

The publication WO 01/68384, in the name of the present applicant,describes a method and a device for marking low surface energyophthalmic lenses using an energization discharge that selectivelyincreases the surface energy corresponding to the cut-outs in a maskplaced between the discharge and the ophthalmic lens to be marked. Thiskind of mask comprises a flexible film applied under mechanical tensionto the surface to be marked or a layer of ink applied to said surfaceand subsequently removed using an appropriate solvent. In a preferredembodiment, the energization discharge is a corona discharge.

In the method described in the PCT application WO 01/68384, theenergization discharge produces a chemical reaction with only theantismudge coating, which breaks the latter's molecular bonds andthereby destroys the integrity of the antismudge coating, so revealingthe higher energy surface of the underlying antireflection coating. Theresulting marking is clearly visible on misting the lens.

The above method is effective and gives good results.

Following surface treatments, the ophthalmic lens undergoes a trimmingoperation that involves machining the edge or periphery of the lens tomatch it to the dimensions of the rim of the frame to which it is to befitted.

Trimming is normally carried out on a grinding machine. During thisoperation, the lens is held by holding members acting axially. Movementof the lens relative to the grinding wheel is numerically controlled toobtain the required peripheral contour. The holding members have to holdthe lens during trimming.

A holding device is placed on the convex face of the lens with aretaining shoe, such as a double-sided adhesive pad, disposed betweenthe holding device and the convex face of the lens. An axial clampingmember clamps the concave face of the lens via a buffer that is normallymade of elastomer.

During trimming, if the holding members are not sufficiently effective,tangential cutting may cause the lens to rotate relative to the holdingmembers, leading to rejection of the trimmed lens. Proper retention ofthe lens depends mainly on good adhesion at the interface between theretaining shoe and the convex face of the lens.

Hydrophobic and/or oleophobic antismudge surface coatings, usually ofthe fluorosilane type, have now become so effective that adhesion at theinterface between the retaining shoe and the convex face of the lens isdegraded or even compromised. This applies to polycarbonate lenses inparticular, whose trimming generates forces much higher than thosenecessary for other materials. This results in a high percentage oflenses rejected because they have not been trimmed correctly.

To overcome this problem, it has been proposed to provide an adhesionlayer on top of the antismudge coating, conferring upon the lens asurface energy greater than that of the outermost layer, i.e. theantismudge coating. This temporary protection layer may be applied tothe whole of the convex face of the lens or only to the central regionthat receives the retaining shoe. Thanks to the temporary protectionlayer, the maximum off-axis error is 2° or even 1° or less.

The protection layer consists of any materials for increasing thesurface energy and adapted to be eliminated after trimming withoutmodifying the optical properties of the lens and the qualities of therelevant face of the lens. The temporary protection layer is preferablya mineral layer, more particularly a layer of a metal fluoride or amixture of metal fluorides, a metal oxide or a mixture of metal oxides,for example magnesium fluoride (MgF₂), lanthanum fluoride (LaF₃),aluminum fluoride (AlF₃) or cerium fluoride (CeF₃) mixtures of aluminaand praseodymium oxide are recommended. A protection layer of the abovekind can be deposited by any conventional method, but preferably byevaporation in a vacuum enclosure, as is generally the case forantireflection and hydrophobic and/or oleophobic antismudge coatings.

The temporary protection layer is preferably from 5 to 50 nm thick. Ifthe protection layer is too thin, the resulting modification of thesurface energy may be insufficient, whereas if it is too thick, there isa risk of mechanical stresses being generated inside the layer, whichmay prejudice the expected properties.

Finally, the temporary protection layer preferably has a minimum degreeof transparency, for example at least 18% or even at least 40%, asdefined in the ISO standard 8980/3, enabling standard power measurementson the lens carrying its protective layer by means of a focimeter.

Alternatively, conventional inks for marking ophthalmic lenses and/orresins constituting the binder of such inks may be used. With organicprotection layers, much greater thicknesses can be obtained, from 5 to150 μm. Alkyde type resins are satisfactory.

Antireflection coatings and hydrophobic/oleophobic coatings aregenerally deposited by evaporation in a vacuum. The lenses on whichantireflection and antismudge coatings have been deposited are placedabove orifices in a turntable in the vacuum enclosure and theirperiphery rests on a ring fastened to the turntable by holding means.The treatment device is situated in the lower portion of the enclosureand comprises a crucible in which the material to be evaporated isplaced and that is generally heated by means of an electron beam or adual effect source, depending on the nature of the material to beevaporated.

The material to be evaporated to constitute a coating layer is depositedon the face of the lens to be treated until the required thickness isobtained, at which point the evaporation of this first material isstopped. The next material is then evaporated. As a general rule, all ofthe coatings are deposited on one face of the lens. then, after turningthe lens over, all of the coatings are deposited on the other face ofthe lens, this set of coatings normally being identical to thatdeposited on the first face of the lens.

Obviously, when treating the second face, the integrity of the layersdeposited on the first face must be protected, especially the integrityof the outermost layer. The hydrophobic and/or oleophobic antismudgecoating is very thin, having a thickness from 2 to 10 nm or even from 2to 5 nm. Now, it is sometimes necessary to treat the face of the lensusing very energetic substances, i.e. substances whose energies exceed0.1 eV, or reactive substances, i.e. substances liable to reactchemically with the surface of the lens. In particular, beforedepositing multilayer antireflection coatings, the ophthalmic lensundergoes surface preparation, such as ionic bombardment (for examplewith rare gases, oxygen, mixtures thereof, nitrogen or air), plasmatreatment or discharge treatment (typically treatment by an oxygenplasma at a pressure of 10⁻² mbar). It may also be necessary to carryout an activation treatment in order to prepare a surface beforedepositing a coating layer, for example to increase the adhesion of thelayer. Similarly, ionic bombardment may be applied during evaporation ofthe materials to improve its mechanical properties and in particular todensify the layer (this is known as ionically assisted deposition(IAD)).

The substances generated are highly energetic and/or reactive and areliable to degrade the deposit on the first face of the lenses and inparticular those situated at the periphery of the turntable. The sameproblem is encountered if the lenses to be treated have an overall shapesimilar to that of the lens when ready for mounting, depending on theframe, the energetic and/or reactive substances then being able to passbetween the circular orifice in the turntable and the peripheral edge ofthe lens to whose first face a deposit has been applied.

To overcome this problem, depositing a temporary protective layer on thethin outermost antismudge layer, i.e. the external layer of the lens, inorder to protect the outermost layer of the first face of the lens whendepositing coating layers on the second face in a vacuum enclosure hasbeen envisaged.

This temporary protection layer must be thick enough to preventdegrading the properties of the thin outermost layer and is chosen as afunction of the surface energy of the substances, which can vary from 40to 150 eV with a current density at the lens surface from 30 to 700μA/cm². The thickness of the protection layer is preferably from 5 nm to10 μm for this application. If the protection layer is a mineral layerdeposited by evaporation, its thickness is preferably from 5 to 200 nm.In all cases, the protection layer must not be too thin, to avoid therisk of insufficiently protecting the thin hydrophobic and/or oleophobicoutermost layer, or too thick, in particular for the essentially mineralprotection layers, to prevent the risk of mechanical stresses appearingwithin the layer, which would be prejudicial to its properties.

The layer used for this purpose may have the same composition as theadhesion layer referred to above. Mixtures of alumina and praseodymiumoxide are also recommended for this purpose.

Organic material temporary protection layers include those based onpolytetrafluoroethylene (PTFE), for example that sold under the trademark TEFLON®.

A multilayer temporary protection coating, and in particular a two-layercoating, may also be envisaged, the first layer being a thin minerallayer (from 5 to 200 nm thick), while the second layer is organic andcan be obtained by depositing and hardening a latex. This layer isthicker, from 0.2 to 10 μm thick.

The organic layer provides good mechanical protection and can be peeledoff easily. The organic layer is selected so that its adhesion to themineral first layer is greater than that to the interface between themineral first layer and the hydrophobic and/or oleophobic layer. Thusthe mineral layer is also removed on peeling off the organic layer.

Now, depositing a temporary protection layer to ensure good adhesionbetween a retaining shoe and the convex face of the lens and/or toprotect the first face of the lens during treatment with highlyenergetic or reactive substances forms a screen or mask in front of thecorona discharge source which prevents the discharge reaching the thinlow surface energy layer through the temporary protection layer in oneor the other of the applications cited above.

It has therefore been necessary to carry out the corona treatment beforedepositing the temporary protection layer, which has involvedtransferring the lens from the vacuum enclosure to the corona treatmentdevice and then returning it to the vacuum enclosure to deposit thetemporary protection layer.

It has been found, unexpectedly, that the corona treatment can becarried out on the thin hydrophobic and/or oleophobic layer through thetemporary protection layer provided that it is less than approximately 5nm thick, i.e. has a thickness that until now has been consideredinsufficient for one or the other of the applications cited above. Itproves that, despite the fact that the temporary protection layer isvery thin, this layer proves adequate in both the applications citedabove.

Thus one aspect of the present invention is a method for marking oneface of an ophthalmic lens of the type including a low surface energyhydrophobic and/or oleophobic outermost layer on a substrate or a highsurface energy coating, wherein a mask having a configurationcomplementary to the required mark is positioned between the face of thelens to be marked and an energizing discharge source adapted to oxidizethe outermost layer in order to reveal the substrate or underlying highenergy coating, which method is characterized in that there is depositedonto said outermost layer a temporary protection layer having a surfaceenergy higher than that of the outermost layer and a thickness of lessthan about 5 nm to enable the discharge to act on the outermost layerthrough the temporary protection layer.

The protection layer is preferably a mineral layer deposited byevaporation and comprises, for example, a metal fluoride or a mixture ofmetal fluorides, such as MgF₂, LaF₂, AlF₃ or CeF₃, or a metal oxide or amixture of metal oxides, such as TiO₂, Al₂O₃, ZrO₂ and praseodymiumoxide and the mixture of metal oxides is a mixture of alumina andpraseodymium oxide.

The temporary protection layer may have a substantially continuousstructure or a discontinuous structure, in particular in the form of ascreen.

In a different embodiment the temporary protection layer is an organicmaterial and is preferably based on polytetrafluoroethylene.

Alternatively, the protection layer consists of a marking ink forophthalmic lenses and/or a polymer constituting a marking ink binder.

The temporary protection layer is preferably eliminated after trimmingthe lens, in particular by an acid solution, by dry wiping or byapplication of ultrasound.

In practice, deposition of the hydrophobic and/or oleophobic outermostlayer on a first face of the lens is preceded by the deposition of oneor more mineral or organic layers, characterized in that at least onestep of treatment by energetic and/or reactive substances capable ofattacking and/or chemically modifying the surface of the first face ofthe lens is effected before the deposition of the mineral or organiclayer(s). The lens can then be turned over to treat its second face byenergetic and/or reactive substances before depositing one or moremineral or organic layers and a hydrophobic and/or oleophobic outermostlayer. A temporary protection layer can then be deposited on thehydrophobic and/or oleophobic outermost layer on the second face of thelens to improve its adhesion to the holding member that cooperates withthis second face during trimming.

The marking as such is carried out using the method described in PCTapplication WO 01/68384. Although the corona discharge source is thepreferred energization source for selectively oxidizing the outermosthydrophobic and/or oleophobic layer, other sources can be used, such asa cold plasma or ultraviolet radiation source for photo-oxidation of themolecules of the hydrophobic and/or oleophobic outermost layer.

The invention is described with reference to the appended drawing, inwhich:

FIG. 1 is a diagrammatic view of low-frequency corona treatmentapparatus for marking a lens, and

FIG. 2 is a partial diagrammatic view of a lens of the inventionfollowing corona treatment through a temporary protection layer.

A lens treated in accordance with the present invention comprises amineral or organic glass substrate. The two faces of the lens carrydifferent layers, some of which are deposited one on top of the other,by evaporation of materials contained in a crucible, using an electrongun or by the Joule effect, in a vacuum enclosure. There may be cited inparticular the Balzers BAK 760 machine equipped with an electron gun, anion gun of the end-Hall, Commonwealth Mark 2 type and a Joule effectevaporation source, or the Leybold 1104 vacuum treatment machineequipped with an electron gun and a Joule effect evaporation source.Before depositing a first layer on a first face, preferably the convexface, that face is treated with the energetic and/or reactivesubstances, in particular by ionic bombardment, for example with a beamof ions of argon and oxygen, using the ion gun, or plasma treatment tochemically modify the surface in order to improve the adhesion of thedeposit.

The first coating usually comprises an antiabrasion layer, in particularof the polysiloxane type corresponding to example 3 of European patentapplication N° 0.614.957, which protects the substrate from scratches,especially if it is a polycarbonate organic substrate, which has a highsurface energy.

Onto this first coating is then deposited a single-layer or multilayerantireflection coating having a high surface energy. A coating of thiskind is preferably a multilayer coating in which the layers aresuccessively of high and low refractive index and may comprise, forexample, a first layer consisting of ZrO₂, a second layer consisting ofSiO₂, a third layer consisting of ZrO₂, and a fourth and final layerconsisting of SiO₂. A coating of this kind is relatively insensitive toenergizing discharges, such as corona, cold plasma or ultravioletirradiation discharges. Because of this, marking by means of suchenergizing discharges leaves the antireflection coating layerssubstantially intact, and in particular the outermost layer. It goeswithout saying that other antireflection coatings may be used, and inparticular those consisting of a plurality of mineral layers. Similarly,other methods of depositing antireflection coating layers may be used,and in particular cathode sputtering or plasma-assisted vapor phasechemical reaction methods.

The hydrophobic and/or oleophobic external coating is then deposited onthe antireflection coating by evaporation in a Joule effect crucible ofan Optool DSX compound from Daikin comprising perfluoropropylene groups.The thickness of this kind of hydrophobic and oleophobic coating is lessthan 10 nm, even 5 nm, and is preferably 2 nm. Its surface energy isless than 14 millijoules/m² and preferably equal to or less than 12millijoules/m².

According to the invention, a temporary protection layer less than 5 nmthick is deposited, also by evaporation, and preferably in the samevacuum enclosure, onto the hydrophobic and/or oleophobic coating, overthe whole of the treated face, to protect it during the treatment of theother face of the lens, or where applicable over a region intended tocome into contact with the retaining shoe, in particular when the convexface is treated in the vacuum enclosure after the concave face andprotection against energetic and/or reactive substances is therefore notindispensable.

The temporary protection layer is a mineral layer consisting of a metalfluoride or a mixture of metal fluorides or a metal oxide or a mixtureof metal oxides, for example. MgF₂ from Merck with a mean particle sizeof 2.5 mm is preferably used, and is placed in the crucible andevaporated by the electron gun. The rate of deposition is approximately0.50 nm/s, and the position takes from 4 to 8 seconds, producing atemporary protection layer from about 2 nm to about 4 nm thick. Thethickness deposited is controlled by a quartz microbalance.

After the temporary protection layer has been deposited, the enclosureis heated and the treatment chamber vented to atmosphere before turningover the lenses. The treatment steps already described are then repeatedon the second face of the lens. The temporary protection layer,preferably of MgF₂, deposited on the convex face is intended to increasethe surface energy thereof to improve adhesion during trimming.

After the coating layers have been deposited on both faces of the lens,the lens is taken out of the enclosure for marking in a low-frequencycorona treatment device 10 shown diagrammatically in FIG. 1 andincluding a Mylar® screen or mask 12 tensioned by a Mylar® tensioningmechanism. This screen includes a cut-out 13 that is complementary tothe pattern that will be marked on the lens 20 and is held by a pivotingarm 15 (represented here in a position at 90° to its normal position tosimplify the diagram) and urged toward a position in which its retainingshoe 16 engages with the center of the convex face 21 of the lens, sothat the corresponding region of the convex face 22 is in intimate andcontinuous contact with the portion of the screen including the markingcut-out.

A Softal-3DT MultiDyne corona discharge device 30 is installed under thescreen inside a housing of which only the top plate 11 is representedand comprises two hook-shaped or D-shaped wire electrodes 31 having astraight portion followed by a semicircular portion. The semicircularportions face each other. The distance between the electrodes and thelens to be treated is approximately 5 mm. This enables treatment of anoval region whose major axis can be up to 65 mm long. These electrodesare connected to the secondary windings 33 of a 12 kV high-tensiontransformer 32. For safety reasons, the secondary windings have agrounded center tap which halves the voltage between the high-tensionconductors and ground. A constant flow of pressurized air is directedbetween the electrodes by a source 35, preferably a fan. The effect ofthis flow of air is to divert the electrical arc 40 and to spread itwith a curvature that is determined by the configuration of theelectrodes. The higher the voltage and the higher the velocity of theflow of air, the more the arc spreads. Arcs are produced for 5 secondsat a constant rhythm of 50 to 60 cycles/second. The continuous arcproduces a corona discharge with very highly charged ions. This energyfield is capable of disintegrating the thin hydrophobic and/oroleophobic coating facing the cut-outs 13 in the screen 12 through theprotection layer deposited on the coating and whose thickness is lessthan about 5 nm, preferably from about to 2 to about 4 nm, and morepreferably about 2 nm. The device includes means (not shown) forregulating the air flow. It can further include a system for filteringand extracting ozone produced in the corona treatment that converts theozone into oxygen, the gas filtered in this way escaping from under thehousing.

FIG. 2 is a diagrammatic partial view to a larger scale of a portion ofthe temporary protection layer 23 on the convex face 22 and thehydrophobic and/or oleophobic layer 24 onto which the temporaryprotection layer is deposited and which includes regions 25disintegrated by the energizing discharge source to expose the surfaceof the outermost layer of the antireflection coating having a highsurface energy. The lens is then trimmed to fit it to the rim of theframe. This trimming of the lens may be carried out on an Essilor Gammagrinding machine, for example, the lens being held between a retainingshoe, in this instance a 25 mm diameter 3M self-adhesive pad thatcooperates with the convex face and an Essilor holding device of thesame diameter. The off-axis error during trimming is less than 1° andtherefore perfectly satisfactory.

The temporary protection layer may then be eliminated by dry wiping witha cotton cloth or in a liquid medium. It is preferably eliminated in aliquid medium using an acid solution, in particular a 0.01 to 1 Nsolution of orthophosphoric acid. This solution may also containcationic or amphoteric surfactants. The lens is dipped into theorthophosphoric acid solution in the ultrasound tank for two minutes atroom temperature and then rinsed with water or isopropyl alcohol anddried. The temperature of the solution may vary, room temperature beingsatisfactory. The above two means may even be combined, namely drywiping followed by cleaning in an aqueous solution with a pHsubstantially equal to 7. This layer can also be eliminated byultrasound in a Branson B2200 E2 60 W ultrasound tank.

EXAMPLE 1

A first coating is deposited comprising a polysiloxane antiabrasionlayer corresponding to example 3 of European patent application N°0.614.957, followed by an antireflection coating comprising a successionof four layers consisting of ZrO₂, SiO₂, ZrO₂, SiO₂, and then a ShinetsuKP801M fluorosilazane coating layer. The lens is then monogrammed withthe corona discharge device described above, the process taking 5seconds.

EXAMPLE 2

A first coating is deposited comprising a polysiloxane antiabrasionlayer corresponding to example 3 of European patent application N°0.614.957, followed by an antireflection coating comprising a successionof four layers consisting of ZrO₂, SiO₂, ZrO₂, SiO₂, and then a DaikinOptool DSX coating layer containing perfluoropropylene groups. The lensis then monogrammed as in example 1.

EXAMPLE 3

A 20 nm thick temporary protection layer of MgF₂ is deposited ontoanother lens prepared as in example 1. The lens is then monogrammed asin example 1, but for 10 seconds. The temporary protection layer is theneliminated by wiping with a Selvyt® polishing cloth.

EXAMPLE 4

The example 3 procedure is followed, with monogramming effected in fiveperiods each of 10 seconds duration, i.e. a total of 50 seconds.

EXAMPLE 5

A 20 nm thick temporary protection layer of MgF₂ is deposited ontoanother lens prepared as in example 2. The lens is then monogrammed asin example 1, but for 10 seconds, after which the temporary protectionlayer is eliminated by wiping with a Selvyt® polishing cloth.

EXAMPLE 6

The procedure of example 5 is followed with monogramming effected infive periods each of 10 seconds duration, i.e. a total of 50 seconds.

EXAMPLE 7

A 2 nm thick temporary protection layer of MgF₂ is deposited ontoanother lens prepared as in example 1. The lens is then monogrammed asin example 1, after which the temporary protection layer is eliminatedby wiping with a Selvyt® polishing cloth.

EXAMPLE 8

A 2 nm thick temporary protection layer of MgF₂ is deposited ontoanother lens prepared as in example 2. The lens is then monogrammed asin example 1, after which the temporary protection layer is eliminatedby wiping with a Selvyt® polishing cloth.

All of the lenses treated as above are then misted cold in order to showthe monogrammed pattern. The monogramming on the lenses of examples 1and 2 is good. The complementary high surface energy regionscorresponding to the cut-outs of the screen are covered with a film ofcondensation comprising large droplets and of dark appearance underambient lighting, whereas on the low surface energy regions protected bythe screen the film of condensation consists of microdroplets of a muchlighter tone.

Misting the lenses of examples 7 and 8 obtains the same good qualitycondensation patterns as with the lenses of examples 1 and 2.Furthermore, the optical and physical qualities of the outermostcoating, i.e. the hydrophobic and/or oleophobic antismudge coating ofthe lens, after elimination of the temporary protection layer as inexamples 7 and 8, are virtually identical to those of the lens beforedepositing the temporary protection layer onto the lenses as in examples1 and 2.

On the other hand, misting the lenses from examples 3 and 5 does notshow up condensation patterns complementary to the cut-outs in thescreen. Similarly, with examples 4 and 6, the misting in the regionscomplementary to the cut-outs of the screen consists of microdropletslarger than those in the regions protected by the screen, but thecontrast between these regions is very low and therefore themonogramming is of mediocre quality.

In the embodiment described, the energizing discharge source is a coronadischarge source. Other energizing discharge sources may be used, suchas a cold plasma source or a source of ultraviolet radiation, forexample.

A cold plasma source may comprise an electrical or microwave dischargeor a luminescent discharge source. An electrical or microwave source canproduce a discharge in a gas such as oxygen, argon, nitrogen, carbontetrafluoride, helium or ammonium at reduced pressures of the order of 1millibar. The duration of the discharge may vary from a few seconds to afew tens of seconds and is preferably of the order of several seconds.Atea manufactures the Matis cold plasma discharge source. It is alsopossible to use a Lectro Treat cold plasma discharge source, whichproduces a hybrid corona discharge at atmospheric pressure.

An ultraviolet radiation source will produce photo-oxidation of themolecules at the irradiated surface. Molecular dissociation is obtainedwith wavelengths of the order of 2357 A° and 1849 A°. A Uvocs surfacedecontamination unit may be used as a source of ultraviolet radiationfor the purposes of the present invention.

Similarly, instead of the screen described in the preferred embodiment,another form of mask may be used, for example a layer of ink applieddirectly to the surface to be marked, as described in the publication WO01/68384 cited above.

Such other energizing discharges are also liable to disintegrateselectively the hydrophobic and/or oleophobic layer, in particular byoxidation or destruction of covalent bonds.

Of course, many modifications may be made to the embodiments describedhereinabove without departing from the scope of the invention.

1. Method for marking one face of an ophthalmic lens of the typeincluding a hydrophobic and/or oleophobic outermost layer on a substrateor an underlying coating having a higher surface energy than thehydrophobic and/or oleophobic outermost layer, wherein a mask having aconfiguration complementary to a required mark is positioned between theface of the lens to be marked and an energizing source adapted toeliminate selectively the outermost layer in order to reveal thesubstrate or underlying coating, and wherein there is deposited ontosaid outermost layer a temporary adhesion enhancing layer for enhancingadhesion of the face of the lens with a lens retaining shoe whentrimming the lens, said temporary adhesion enhancing layer having asurface energy higher than that of the outermost layer and a thicknessof less than about 5 nm and wherein the energizing source acts on theoutermost layer through the temporary adhesion enhancing layer. 2.Method according to claim 1, wherein the thickness of the temporaryadhesion enhancing layer is from approximately 2 nm to approximately 4nm.
 3. Method according to claim 1 wherein the adhesion enhancing layeris a mineral layer.
 4. Method according to claim 1, wherein the adhesionenhancing layer comprises a metal fluoride or a mixture of metalfluorides or a metal oxide or a mixture of metal oxides.
 5. Methodaccording to claim 4, wherein the metal fluoride is MgF₂, LaF₂, AlF₃ orCeF₃.
 6. Method according to claim 4, wherein the oxide is selected fromTiO₂, Al2O₃, ZrO₂ and praseodymium oxide and the mixture of alumina andpraseodymium oxide.
 7. Method according to claim 1, wherein the adhesionenhancing layer is deposited by evaporation.
 8. Method according toclaim 1, wherein the temporary adhesion enhancing layer is deposited ona region of the face intended to be in contact with the lens retainingwhen trimming the lens.
 9. Method according to claim 1, wherein theadhesion enhancing layer has a substantially continuous structure. 10.Method according to claim 1, wherein the adhesion enhancing layer has adiscontinuous structure.
 11. Method according to claim 1, wherein theadhesion enhancing layer takes the form of a screen.
 12. Methodaccording to claim 1, wherein the temporary adhesion enhancing layercomprises polytetrafluorethylene.
 13. Method according to claim 1,wherein the adhesion enhancing layer comprises a marking ink forophthalmic lenses and/or polymer constituting a marking ink binder. 14.Method according to claim 1, wherein the hydrophobic and/or oleophobicoutermost layer comprises fluorinated groups.
 15. Method according toclaim 1, wherein the lens comprises an antireflection coating onto whichthe hydrophobic and/or oleophobic outermost layer is deposited. 16.Method according to claim 15, wherein the hydrophobic and/or oleophobicoutermost layer includes a plurality of layers.
 17. Method according toclaim 1, wherein the temporary adhesion enhancing layer is removed by anacid solution.
 18. Method according to claim 1, wherein the temporaryadhesion enhancing layer is removed by dry wiping.
 19. Method accordingto claim 1, wherein the temporary adhesion enhancing layer is removed byapplication of ultrasound.
 20. Method according to claim 1, wherein thetemporary adhesion enhancing layer is removed and thereafter a cleaningstep is carried out using an aqueous solution with a pH substantiallyequal to
 7. 21. Method according to claim 1, wherein the deposition ofthe hydrophobic and/or oleophobic outermost layer on a first face of thelens is preceded by the deposition of one or more mineral or organicslayers, wherein at least one step of treatment by energetic and/orreactive substances capable of attacking and/or chemically modifying thesurface of the first face of the lens is effected before the depositionof the mineral or organic layer(s).
 22. Method according to claim 21,wherein the lens is turned over to treat its second face by energeticand/or reactive substances before depositing one or more mineral ororganic layers and a hydrophobic and/or oleophobic outermost layer. 23.Method according to claim 22, wherein a temporary adhesion enhancinglayer is deposited on the hydrophobic and/or oleophobic outermost layeron the second face of the lens.
 24. Method for marking one face of anophthalmic lens of the type including a hydrophobic and/or oleophobicoutermost layer on a substrate or an underlying coating having a highersurface energy than the hydrophobic and/or oleophobic outermost layer,wherein a mask having a configuration complementary a desired mark ispositioned between the face of the lens to be marked and an energizingsource adapted to eliminate selectively the outermost layer in order toreveal the substrate or underlying coating, and wherein there isdeposited onto said outermost layer a temporary adhesion enhancinglayer, said adhesion enhancing layer having a surface energy higher thanthat of the outermost layer and a thickness of less than about 5 nm,selectively eliminating the outermost layer through the temporaryadhesion enhancing layer by action of the energizing source, andremoving the adhesion enhancing layer from the ophthalmic lens after theoutermost layer has been selectively eliminated from the lens to producethe desired mark and after the ophthalmic lens has been trimmed to thedesired contour.